0.8 array notification

[kevinpschaaf]

Removes use of ArrayObserve.observe. Instead, users must use this.push(), etc. on elements to mutate arrays. Collection is also no longer observable; simply stands as a store of key->item and item->key mappings for arrays.

Renames getPathValue and setPathValue to get and set.

get and set can now take an array of path parts, to avoid needing to concat, e.g. set([items', 4, 'name'], 'bob);, and also does automatic array index-to-key mapping when notifying path (4 in example would be replaced with the key for items[4] when notifying).

Renames _data to __data__ to avoid collision with user data.

[arthurevans]

What's the motivation for this change? Is Array.observe too heavy-weight, or just not working right?

[kevinpschaaf]

@arthurevans Prior to this change, we used Array.observe (on Chrome) but on all other browsers overrode array instances with patched push/pop/etc. methods to be able to observe when changes occurred (remember, we're avoiding the observe-js polyfill overhead for Polymer proper). The patching approach was not only intrusive, but led to a hard-to-explain API w.r.t. making changes to structured data (if you want to set set this.items[4] and have Polymer see it, you need to use this.set, but if you want to push onto this.items, you could just push onto the array). Now, all mutation of objects/arrays should be done through Polymer.Base API's:

• get
• set
• push
• pop
• shift
• unshift
• splice

[sorvell]

LGTM